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Test Code ORXNA Orexin-A/Hypocretin-1, Spinal Fluid

Reporting Name

Orexin-A/Hypocretin-1, CSF

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Useful For

Aiding in the diagnosis and differentiation of type 1 narcolepsy from other causes of hypersomnolence

 

This assay is not intended for use as a screening test.

Method Name

Radioimmunoassay (RIA)


Ordering Guidance


Orexin-A (hypocretin-1) deficiency is the hallmark of narcolepsy type 1. The diagnostic criteria for type 1 narcolepsy include the presence of cataplexy and/or measured cerebrospinal fluid orexin-A/hypocretin-1 concentrations less than or equal to 110 pg/mL. Alternative testing for narcolepsy type 1 includes mean latency of 8 minutes in the clinical multiple sleep latency test, with evidence of sleep-onset rapid eye movement periods and cataplexy.



Specimen Required


Patient Preparation: Patient should not have recently received radioisotopes, either therapeutically or diagnostically, due to potential assay interference.

Collection Container/Tube: Sterile vial

Submission Container/Tube: Plain vial with no additives

Specimen Volume: 1.5 mL

Pediatric Volume: 0.5 mL

Collection Instructions:

1. Obtain aliquot from second collection vial (preferred, not required).

2. Hemolyzed specimens will give false-positive results. Specimens should be centrifuged to remove any red cells prior to shipping.


Specimen Type

CSF

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
CSF Frozen (preferred) 120 days
  Refrigerated  7 days
  Ambient  72 hours

Reject Due To

Gross hemolysis Reject

Reference Values

Normal individuals: >200 pg/mL

 

Previous literature has defined cerebrospinal fluid orexin-A/hypocretin-1 concentrations of 110 pg/mL or below as being consistent with narcolepsy type 1-(Mignot E. Arch Neurol. 2002:59;1553-1562). Concentrations between 111 pg/mL and 200 pg/mL are considered intermediate and have limited diagnostic utility for narcolepsy, as they may be representative of other neurological disorders. Concentrations above 200 pg/mL are considered normal.

Interpretation

The diagnostic criteria for type 1 narcolepsy in the International Classification of Sleep Disorders (3) include the presence of hypersomnia, cataplexy (episodes of muscle weakness in response to emotional stimuli) and measured cerebrospinal fluid (CSF) orexin (hypocretin-1) concentrations less than or equal to 110 pg/mL.

 

Orexin (hypocretin-1) CSF concentrations have been classified into 3 categories in the literature. They include low (≤110 pg/mL), which is indicative of type 1 narcolepsy; intermediate (ranges between 111-200 pg/mL); and normal (>200 pg/mL). Previous studies have shown that 106 of 113 patients with clinically defined type 1 narcolepsy exhibited low (<110 pg/mL) orexin concentrations. In another study, all 48 healthy individuals exhibited orexin (hypocretin-1) CSF concentrations above 200 pg/mL.

Day(s) Performed

Twice monthly (Second and fourth Monday)

Report Available

3 to 32 days

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

83519

LOINC Code Information

Test ID Test Order Name Order LOINC Value
ORXNA Orexin-A/Hypocretin-1, CSF 91670-0

 

Result ID Test Result Name Result LOINC Value
604230 Orexin-A/Hypocretin-1, CSF 91670-0

Forms

If not ordering electronically, complete, print, and send a Neurology Specialty Testing Client Test Request (T732) with the specimen.